Tips on how to fall asleep?

I'm starting school again in a month and i have a difficult time waking up in the morning. Why? Because i can't get to sleep the night before. I want to be able to wake up at 6:00 am but I can't because i can't seem to fall asleep until 4:30 am. Once I start to feel tired I go to bed but then I can't fall asleep so I listen to music but that doesn't work. My back is often sore when I lay down and a few days ago I had shoulder pain- I ume both are related to either my lack of sleep or lack of quality in my sleep. Also, I've been a lot moodier because i can't get a decent sleep schedule and I've been breaking out more which is related to the amount of sleep I get. I try to drink tea and sit down but sitting down and trying to relax doesn't do anything and then when I watch TV or go on the computer my eyes feel like they are drying out but I still can sleep- plus I've heard that watching TV or going on the computer before you sleep can decrease the quality of sleep you get. I often end up laying in bed for 2 hours before I finally fall asleep. Does anyone have any tips? Is medication for this necessarily or is it something I'm doing? And if it's the mattress how much would a new mattress cost?